Dietary manipulation of the disappearance of trans-octadecenoates in rat tissues.

Abstract

SummaryThe effects of dietary manipulations on the fate of trans octadecenoates deposited in the tissues of rats were examined . Male rats were fed on a 15% fat diet containing trans-octadecenoic acids (46 .6% of total fatty acids) for 35 days followed by various diets free of trans-fatty acids. After removal of traps-fatty acids from the diet, there were phased disappearances of trans-octadecenoates from the circulation; a rapid and broad reduction in one day and a slow and gradual reduction thereafter . The rate of the initial reduction in serum trans-octadecenoates was highest on a high fat (20%) diet in relation to low fat (1 or 5%) diets . However, the disappearance rate at the later stage was apparently the same among the various groups and traps-fatty acid contents in the serum declined to about 10% of the initial value in 2 weeks and thereafter . After 35 days, the concentration of traps-octadecenoates remaining in the adipose tissue was markedly lower in rats fed on a high protein (40%) diet . The effects of dietary fat type and cholesterol on the fate of serum trans-octadecenoates were virtually the same, but livers from rats fed on the cholesterol-free safflower oil diet contained more trans-fatty acids than those from rats fed on the corresponding olive oil diet. Thus, the amounts of traps-fatty acids stored in the tissues cannot be merely predicted from serum levels . It seems that both dietary fat and protein affect the metabolic rate of trans octadecenoates in rats.